Cutting tools, etc. are provided with single- or multi-layer hard coatings made of carbides, nitrides and carbonitrides of Al, Cr, Ti and Si, or oxides of Al, etc., to improve hardness, wear resistance, lubrication, seizure resistance, etc. Particularly because coatings of composite nitrides of Ti and Al (TiAlN) exhibit excellent wear resistance, they are formed on cutting tools of high-hardness materials such as high-speed steel, hardened steel, etc.
JP 2003-71610A discloses a cutting tool having a multi-layer coating, as a hard coating having higher wear resistance than TiAlN, which is formed by alternately laminating two types of layers having different compositions plurality times, both within a composition range represented by (TiaAlbCrc)(C1-dNd), wherein a, b and c represent the atomic ratios of Ti, Al and Cr, respectively, and d represents the atomic ratio of N, meeting 0.02≦a≦0.30, 0.55≦b≦0.765, 0.06≦c,a+b+c=1, and 0.5≦d≦1, or 0.02≦a≦0.175, 0.765≦b, 4(b-0.75)≦c, a+b+c=1, and 0.5≦d≦1. Although this multi-layer coating has excellent wear resistance, it falls to sufficiently meet an increasingly mounting demand to provide cutting tools with higher wear resistance and/or seizure resistance.
JP 2004-238736A discloses a hard coating formed by an arc-discharge ion plating method, which has a composition comprising a metal component represented by AlxCr1-x wherein x represents an atomic ratio meeting 0.45≦x≦0.75, and a non-metal component represented by N1-α-β-γBαCβOγ, wherein α, β and γ respectively represent atomic ratios meeting 0 ≦α≦0.15, 0≦β≦0.35, and 0.01≦γ≦0.25, the hard coating having the maximum X-ray diffraction intensity in a (200) plane or a (111) plane, and the bonding energy of Al and/or Cr and oxygen in a range of 525-535 eV in X-ray electron spectroscopy. It further describes that a hard coating formed by laminating two layers having different compositions within the above ranges has not only improved hardness and wear resistance, but also improved adhesion to a substrate. However, it still falls to sufficiently meet an increasingly mounting demand to provide cutting tools with higher wear resistance and/or seizure resistance.
JP 7-205361A discloses a member having a hard coating formed by laminating at least one compound selected from the group consisting of nitrides, oxides, carbides, carbonitrides and borides of metal elements of Groups IVa, Va and VIa, Al and Si, and a nitride, an oxide, a carbide, a carbonitride and/or a boride of two types of metal elements selected from the group consisting of metal elements of Groups IVa, Va and VIa, Al and Si, at a period of 0.4-50 nm to a total thickness of 0.5-10 μm. Although this hard coating has excellent wear resistance, it still fails to sufficiently meet an increasingly mounting demand to provide cutting tools with higher wear resistance and/or seizure resistance.